.beta.-Damascenone, an alicyclic ketone having the formula ##STR4## is a particularly well-appreciated fragrant and flavourant compound. The use thereof as perfuming or flavourmodifying ingredient is the object of several patents, namely U.S. Pat. No. 3,975,310, Swiss Pat. Nos. 520,479 and 509,399.
Many syntheses have been proposed in the past for preparing .beta.-damascenone, the most interesting ones being cited hereinafter:
dehydrogenation of the corresponding cyclohexenic compound, viz. .beta.-damascone (see Swiss Patent No. 505,773); PA0 treatment of 1-(2,6,6-trimethyl-1,2-epoxy-cyclohexyl)-but-2-en-1-one with an acidic dehydrating agent (see DE-AS No. 20 65 322); and PA0 treatment of 4-(2,6,6-trimethyl-1-hydroxy-cyclohex-2-en-1-yl)-but-3-yn-2-ol with an acidic dehydrating agent (see DE-PS No. 22 42 751).
Despite the existence of several synthetic methods, there could exist one day certain difficulties of supply of the market, mainly due to the large increase of interest shown by the perfume and flavour industry for this particularly useful ingredient.
It is therefore necessary either to improve the yield of the existing methods or to elaborate new and original syntheses, namely syntheses starting from cheaper or more accessible raw materials. The invention provides an efficient solution to this problem.